Build a Nordic nRF52 BLE GATT Server and Android App for Temperature Tracking

Implementing a Nordic nRF52 BLE GATT Server with a Custom Android App for Real-Time Temperature Monitoring

This tutorial will guide you through the process of implementing a Bluetooth Low Energy (BLE) GATT server using the Nordic nRF52 microcontroller, paired with a custom Android application to monitor temperature data in real-time. You’ll learn the prerequisites, required parts, and step-by-step instructions to set up your project.

Prerequisites

• Basic knowledge of embedded programming and Android development.
• Nordic nRF52 development kit (e.g., nRF52832, nRF52840).
• Android Studio installed on your computer.
• nRF Connect app for testing BLE services.
• Temperature sensor (e.g., DS18B20 or similar).
• Wiring tools (jumper wires, breadboard, etc.).

Parts/Tools

• Nordic nRF52 Development Kit
• Temperature Sensor
• Android Studio
• nRF Connect App
• Jumper Wires and Breadboard

Steps

1. Set Up the Hardware
   1. Connect the temperature sensor to the nRF52 kit.

      
                      // Example wiring for DS18B20
                      VCC -> 3.3V
                      GND -> GND
                      DATA -> P0.02
                      

2. Install Required SDKs
   1. Download and install the latest version of the Nordic SDK.
   2. Set up the development environment by following the Nordic documentation.
3. Create the GATT Server
   1. Open your Nordic SDK project.
   2. Implement the GATT server with a custom service for temperature data.

      
                      #define TEMPERATURE_SERVICE_UUID 0x1809
                      #define TEMPERATURE_CHAR_UUID 0x2A1C
      
                      // Initialize GATT service
                      void gatt_service_init(void) {
                          // Add service and characteristic
                          // Code to add temperature service
                      }
                      

4. Read Temperature Data
   1. Integrate the temperature sensor reading into your GATT server.

      
                      float read_temperature(void) {
                          // Code to read from the temperature sensor
                      }
                      

   2. Update the characteristic value with the current temperature.

      
                      void update_temperature_value() {
                          float current_temp = read_temperature();
                          // Code to update GATT characteristic
                      }
                      

5. Build and Flash the Firmware
   1. Compile your project in the IDE.
   2. Flash the firmware to the nRF52 development kit.
6. Create the Android App
   1. Start a new Android project in Android Studio.
   2. Add Bluetooth permissions to the AndroidManifest.xml:

      
                      <uses-permission android:name="android.permission.BLUETOOTH" />
                      <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
                      <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
                      

   3. Implement the BLE scanning and connection logic.

      
                      BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
                      // Code to start scanning for devices
                      

7. Retrieve Temperature Data
   1. Connect to the GATT server from the Android app.
   2. Subscribe to notifications for temperature updates.

      
                      // Code to enable notifications for temperature characteristic
                      

8. Test the Application
   1. Use the nRF Connect app to ensure that the GATT server is operational.
   2. Run your Android app and check for real-time temperature updates.

Troubleshooting

• Device Not Found: Ensure Bluetooth is enabled on your mobile device and that the nRF52 is powered on.
• No Updates Received: Confirm the characteristic notifications are enabled on both server and client sides.
• Inaccurate Temperature Readings: Verify the sensor connections and ensure the sensor is functioning correctly.

Conclusion

In this tutorial, you have learned how to implement a BLE GATT server using the Nordic nRF52 microcontroller and a custom Android application for real-time temperature monitoring. By following these steps, you can create a functional and responsive system that can be expanded for other applications as needed.